Process for the manufacture of moulded articles that are partly colored or have regions of different colors

ABSTRACT

For the fast and rational manufacture of moulded articles, specifically contact lenses, that are partly colored or have regions of different colors, by the casting process, measured amounts of two or more crosslinkable materials of different colors are introduced into the casting mould in the uncrosslinked stated unmixed and, after closing the casting mould, are crosslinked together. By suitably controlling the introduction of the different crosslinkable materials with regard to location and/or time the merging of the colors and the transitions between the colors in the contact lens are influenced in a controlled manner.

BACKGROUND OF THE INVENTION

The invention relates to a process for the manufacture of mouldedarticles that are partly coloured or have regions of different coloursaccording to the preamble of the independent claim and to a mouldedarticle manufactured by the process, having at least two regions,especially annular regions, of different colours. The invention relatesspecifically to the manufacture of optical moulded articles, especiallycontact lenses.

Coloured contact lenses are very common. In many cases, there is a needfor the contact lenses not to be coloured over their entire area but tobe coloured only in a central region while the peripheral region is tobe substantially transparent.

For the manufacture of contact lenses of uniform colour throughout it isknown to use an appropriately dyed monomer mixture from which thecontact lenses are then manufactured in conventional manner, especiallyby the casting process. That casting process is described inter alia inU.S. Pat. No. 5,252,056. It is not possible in that manner, however, tomanufacture contact lenses having partly coloured regions or regions ofdifferent colours.

Various processes are known for the manufacture of partly colouredcontact lenses. According to one known process, disclosed, for example,in U.S. Pat. No. 4,553,975, a hydrated contact lens is masked at itsperiphery and immersed in a dyeing bath. The dyeing process typicallylasts from 25 to 65 minutes and is carried out at temperatures ofapproximately 44° C. Subsequently, the dye has to be fixed and thecontact lens has to be extracted in a time-consuming manner. In anotherknown process, described inter alia in U.S. Pat. No. 5,352,245, a drycontact lens manufactured by the casting process is printed with a stampwhile it is still on the male half of the casting mould. After theprinting operation, the dye has to be fixed and the contact lens has tobe hydrated and extracted in a time-consuming manner. A feature commonto both known processes, therefore, is that a (colourless) contact lenshas to be manufactured first and then has to be dyed in further steps ina time-consuming manner.

By means of the invention a process of the generic kind is to be soimproved that it does not require fixing of the dye and extraction ofthe moulded article and that consequently makes possible simpler andsubstantially faster manufacture of moulded articles, especially opticalmoulded articles and specifically contact lenses, that are partlycoloured or have regions of different colours.

According to the invention, the process that solves that problem is onein which measured amounts of two or more crosslinkable materials ofdifferent colours are introduced into the casting mould in theuncrosslinked state unmixed, and, after closing of the casting mould,are crosslinked.

By means of those measures according to the invention the mouldedarticle, specifically the contact lens, is given its coloration duringits actual manufacture by the casting process and the laboriousafter-treatment that is otherwise customary becomes unnecessary. As aresult, the process is especially fast and is particularly suitable forthe rational mass production required, for example, in the case ofso-called daily disposable contact lenses.

Other advantageous measures and preferred forms of the process will beapparent from the dependent claims. By means of those measures it ispossible to influence the distribution of the differently colouredregions and the merging of the colours and the transitions between thecolours in a controlled manner.

DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to Examplesand with reference to the drawings in which:

FIG. 1 shows a section through a casting mould suitable for carrying outthe process of the invention,

FIG. 2 shows a section through a metering device suitable, by way ofexample, for carrying out the process of the invention,

FIG. 3 shows a section, analogous to FIG. 2, through a slightly modifiedmetering device,

FIG. 4 is a schematic representation of a colour distribution in acontact lense manufactured according to a first embodiment of theprocess of the invention,

FIG. 5 is a schematic representation of a colour distribution in acontact lense manufactured according to a second embodiment of theprocess of the invention,

FIG. 6 shows a schematic representation of a solution droplet in theopen casting mould,

FIG. 6a is a schematic representation of the colour distribution in acontact lense manufactured from the solution droplet shown in FIG. 6,

FIG. 7 shows a schematic representation of an other solution droplet inthe open casting mould, and

FIG. 7a is a schematic representation of the colour distribution in acontact lense manufactured from the solution droplet shown in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

The following explanations relate, purely by way of example, only to themanufacture of contact lenses. They apply analogously, however, also tothe manufacture of other optical moulded articles and moulded articlesquite generally.

The process of the invention utilises, for example, a known castingprocess as described, for example, in EP-A-0 637 490. In that castingprocess, a measured amount of a crosslinkable material is introducedinto an open casting mould in the uncrosslinked state by means of asuitable metering device. FIG. 1 shows an assembled casting mould 40 ofthat kind. It comprises essentially two mould halves, namely a femalemould half 41 and a male mould half 42. The concave moulding surface 43of the female casting mould half 41 determines the geometry of the frontsurface of a contact lens to be manufactured. The male casting mouldhalf 42 has a hat-like shape with a convex moulding surface. The convexmoulding surface 44 determines the geometry of the rear surface of acontact lens to be manufactured.

The two casting mould halves 41, 42 are usually manufactured by theinjection-moulding process, a thermoplastic material, preferablypolypropylene, usually being used as the mould material. More recently,however, preference has also been given to the use of casting mouldsmade of glass or quartz glass and also of metal.

After a measured amount of a crosslinkable material suitable for themanufacture of contact lenses has been introduced into the femalecasting mould half 41, the casting mould is closed, the crosslinkablematerial is crosslinked by exposure to a suitable form of energy,usually UV light, the casting mould is opened again and the finishedcontact lens is removed from the casting mould. It is also possible,however, to leave the finished contact lens in one of the casting mouldhalves and to use that mould half as part of the packaging. Such castingmethods for the manufacture of contact lenses and apparatus suitable forthat purpose are known in general (see, for example, U.S. Pat. No.5,252,056 already mentioned) and therefore do not require furtherexplanation.

Crosslinkable materials suitable for the manufacture of contact lensesare known to one skilled in the art in great number. There areunderstood by crosslinkable materials in this context, for example,monomers or monomer mixtures and solutions thereof, especially aqueoussolutions, and preferably water-soluble, uncrosslinked polymers. Asuitable monomer is, for example, 2-hydroxyethyl methacrylate (HEMA) asdescribed inter alia in U.S. Pat. No. 4,073,577. Also suitable, forexample, are monomer mixtures containing HEMA, as are described, forexample, in U.S. Pat. No. 4,123,407. When using monomers there is,however, the disadvantage that subsequent extraction is required.Especially suitable as uncrosslinked materials, therefore, areuncrosslinked water-soluble polymers and solutions thereof.

Water-soluble polymers are especially derivatives of polymeric 1,2- or1,3-diols, more especially derivatives of polyvinyl alcohol (PVA), orderivatives of copolymers of PVA. The derivatisation of corresponding1,3-diols, such as PVA, is suitably carried out by modification of aportion of the 1,3-diol groups with side-chains that containcrosslinkable groups, especially vinylic groups. One suitablederivatisation comprises, for example, reacting portions of the 1,3-diolgroups to form cyclic ketals that contain an olefinically unsaturated,electron-attracting, copolymerisable radical.

Especially suitable representatives of correspondingly derivatised PVAare, for example, pre-polymers, which are derivatives of a polyvinylalcohol having a molecular weight of approximately at least 2000 thatcomprises from approximately 0.5 to approximately 80%, based on thenumber of hydroxyl groups of the polyvinyl alcohol, units of formula I##STR1## wherein R is lower alkylene having up to 8 carbon atoms,

R¹ is hydrogen or lower alkyl, and

R² is an olefinically unsaturated, electron-attracting, copolymerisableradical having preferably up to 25 carbon atoms,

as are disclosed in EP-A-0 641 806.

R² is, for example, an olefinically unsaturated acyl radical of theformula R³ --CO-- wherein

R³ is an olefinically unsaturated copolymerisable radical having from 2to 24 carbon atoms, preferably from 2 to 8 carbon atoms and especiallyfrom 2 to 4 carbon atoms.

In another embodiment, the radical R² is a radical of formula II

    --CO--NH--(R.sup.4 --NH--CO--O).sub.q R.sup.5 --O--CO--R.sup.3(II)

wherein

q is zero or one and

R⁴ and R⁵ are each independently lower alkylene having from 2 to 8carbon atoms, arylene having from 6 to 12 carbon atoms, a saturatedbivalent cycloaliphatic group having from 6 to 10 carbon atoms,arylenealkylene or alkylenearylene having from 7 to 14 carbon atoms, orarylenealkylenearylene having from 13 to 16 carbon atoms, and wherein

R³ is as defined above.

The variables mentioned above have especially the definitions disclosedin detail in EP-A-0 641 806, the relevant disclosure of which isherewith incorporated into the description of the present invention.

Polymer solutions that are specifically suitable for the presentinvention are prepared, for example, according to Example 13 of EP-A-0641 806. According to that Example, 300 g of PVA (e.g. Moviol Hoechst4-88) are placed in a 2-liter double-walled reactor equipped withstirrer and thermometer, 800 g of deionised water are added and themixture is heated, with stirring, at 95° C. After one hour, everythinghas dissolved to give a clear solution and the solution is cooled to 20°C. 27 g (0.155 mol) of methacrylamidoacetaldehyde-dimethylacetal, 440 gof acetic acid, 100 g of conc. hydrochloric acid (37%) and a sufficientamount of deionised water to produce a reaction solution of 2000 g intotal (in the actual case: 333 g) are added. The mixture is stirred at20° C. for 20 hours. The change in the acetate content can be determinedby titration of the acetic acid.

The isolation can be carried out by means of ultrafiltration: thereaction mixture is cooled to 15° C. and adjusted to pH 3.6 with aqueousNaOH (5%). The polymer solution is filtered over a 0.45 μm filter andpurified by ultrafiltration. The ultrafiltration is carried out by meansof a 1KD Omega membrane from Filtron. Ultrafiltration is carried outuntil a residual content of sodium chloride of 0.004% is obtained.Before purification is completed, the solution is adjusted to pH 7 with0.1N sodium hydroxide solution. After concentration, there are obtained1995 g of a 14.54% polymer solution (92% of the theory); N content(Kjendahl determination)=0.683%, acetate content (determined byhydrolysis)=2.34 mol. equiv./g, inherent viscosity: 0.310, double bonds:0.5 mol. equiv./g (determined by micro-hydrogenation), free hydroxygroups (determined by re-acetylation): 15.3 mol. equiv./g, GPC analysis(in water): mol. wt.=19 101, mol. no. 7522, mol. wt./mol. no.=2.54.

The isolation can also be carried out by means of precipitation: thereaction mixture is adjusted to pH 3.6 with triethylamine andprecipitated in acetone in a ratio of 1:10. The precipitate is separatedoff, dispersed twice with ethanol and once with acetone and dried. Theproduct so obtained has the same properties as that obtained byultrafiltration.

The methacrylamidoacetaldehyde-dimethylacetal mentioned is obtained asfollows: in a 3-liter reactor equipped with stirrer and cooling means,220 g (5.5 mol) of sodium hydroxide are dissolved in 300 g of water and700 g of ice. The sodium hydroxide solution is cooled to 10° C. and 526g (5.0 mol) of aminoacetaldehyde-dimethylacetal and 50 mg of4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (radical inhibitor) areadded. To this solution there are slowly added over a period of 3.5hours at 10° C. 548.6 g (5.5 mol) of methacrylic acid chloride. When theaddition is complete, the pH value slowly falls to 7.2 and no more aminecan be detected by GC. The reaction mixture is extracted with 500 ml ofpetroleum ether in order to remove impurities and the aqueous phase issaturated with sodium chloride and extracted three times with 500 ml oftert-butyl methyl ether. The organic phase is dried with magnesiumsulfate, filtered and concentrated using a rotary evaporator. Theresulting 882.2 g of yellowish oil are slowly stirred by means of anUltraturax into 2000 ml of petroleum ether at -10° C. The productcrystallises and is filtered off and dried to yield 713.8 g ofmethacrylamidoacetaldehyde-dimethylacetal (86% of the theory), meltingpoint 30-32° C., according to GC the product is 99.7% pure. A colourlesspolymer solution is prepared according to the example given above andused in the form of a 15% by weight aqueous solution to prepare a sol.

A coloured polymer solution is prepared, for example, by stirring X g ofa 15% by weight polyvinyl alcohol (PVA) solution (in accordance with theexample given above) first for one minute with 5.0 ml of a 0.5% byweight sodium carbonate solution and then for three minutes with asolution of Y mg of Duasyn-Blau-R-KG in Z ml of water. After titrationwith 0.01N hydrochloric acid to pH 7, the solution is twice diluted with400 ml of water each time and ultrafiltered over a 3kD membrane(Filtron) in an ultrafiltration cell (Berghof). The 15% by weightcoloured polymer solution is processed to form a sol. Examples offigures for X, Y and Z are given in Table 1.

To prepare the sol, 30 ml of a 15% by weight aqueous PVA solution and ofthe coloured polymer solution are concentrated using a rotary evaporatorat 100 mbar and 40° C. to a solids content of 33% by weight. Thissolution is stirred intensively with 1.35 ml of a 1% by weight aqueousIrgacure 2959 solution (photoinitiator). The solution is introduced intopolypropylene disposable syringes having a Luerlock connection, and theair bubbles in the solution are removed by centrifugation at 6000 g (10min).

The expression "of different colours" is used to include also uncolouredor colourless crosslinkable materials and uncoloured or colourlessregions of contact lenses. This means, for example, that a coloured andan uncoloured polymer solution are referred to as being of differentcolours. By the expression "measured amount" there is understood theusual amount required to fill the casting mould satisfactorily, it alsobeing possible to provide for over-filling.

For the sake of simplicity, the process of the invention is describedbelow with reference to an example in which only two crosslinkablematerials of different colours, especially polymer solutions, are used,namely an uncoloured solution and a coloured solution. In principle,however, the number of crosslinkable materials of different colours thatcan be used in the process of the invention, and hence the number ofregions of the finished moulded article having different colours, mayalso be larger. It is also possible to use in place of the preferredpolymer solutions mentioned other crosslinkable materials describedhereinbefore under the term crosslinkable materials.

The introduction of the polymer solutions into the open casting mould40, in this case the female mould half 41, is carried out by means of ametering device 50 shown, for example, in FIG. 2. The metering device 50comprises a metering needle, designated 2 in its entirety, and a holdingblock 20. For a better understanding the metering needle 2 has beenshown on an enlarged scale relative to the holding block 20. Themetering needle 2 contains two coaxial metering nozzles, namely an innernozzle 3 and an outer, annular nozzle 4. The inner nozzle 3 is separatedby a partition wall 5 from the outer, annular nozzle 4 which surroundsit coaxially.

The metering needle 2 is fixed in the holding block 20 preferably bymeans of adhesive (for example an epoxy-based adhesive). The holdingblock 20 consists essentially of a lower part 21 and an upper part 23.The upper part 23, the lower boundary surface of which is provided witha recess 25, is fixedly mounted on the lower part 21, preferably byadhesive. The upper end of the outer, annular nozzle 4 ends flush withthe parting surface 22 between the upper part 23 and the lower part 21.

The upper part 23 further has two bores, each of which leads at itsouter end into a connection piece 26 to which the mentioned disposablesyringes 27 with Luerlock connection containing the polymer solutionsare detachably coupled. One of the bores receives the partition wall 5,which surrounds the inner nozzle 3, so that the inner nozzle 3 and thepartition wall 5 extend into the associated connection piece 26.Accordingly, the inner nozzle 3 and the partition wall 5 are longer thanthe outer, annular nozzle 4. The second bore in the upper part 23 isprovided with a tube 29, one end of which leads into the associatedconnection piece 26 and the other end of which ends flush with theboundary surface of the recess 25. In this manner, the two polymersolutions of different colours are introduced into the casting mouldhalf 41 separately. The metering device described herein is merely anexample. Any other metering devices can, of course, be used for carryingout the process of the invention.

By means of the metering device 50 a measured amount of the one polymersolution--either of the uncoloured polymer solution 6 or of the colouredpolymer solution 7--is introduced into the casting mould half 41 fromthe associated disposable syringe 27 through the inner nozzle 3 and ameasured amount of the other polymer solution is introduced into thecasting mould half 41 from the associated disposable syringe 27, throughthe tube 29, through the cavity formed by the recess 25 and through theouter, annular nozzle 4. The two polymer solutions can be introducedinto the casting mould half 41 simultaneously, with a partial overlap intime or separately in time. During the introduction, the metering needle2 can also be moved relative to the casting mould 40 or the castingmould half 41 simultaneously or offset in time. The metering needle 2may be moved in the direction of its longitudinal axis so that, forexample, the metering needle 2 is always situated, throughout theintroduction process, at the surface of the solution droplet beingproduced. In another example, the metering needle 2 may also be immersedin the solution droplet being produced. It is furthermore possible forthe metering needle 2 to be moved transversely to its longitudinal axis.It is thereby possible, for example, for the polymer solutions to bedistributed over regions of the casting mould or for the polymersolutions of different colours to be deposited in different regions ofthe casting mould.

These measures, the parameters of which are each optimised in anempirical manner, and a suitable viscosity of the crosslinkable polymersolutions have the effect that the two polymer solutions mix as littleas possible in the open casting mould 40. This is shown symbolically inFIG. 2 for a first embodiment of the process of the invention. In theopen casting mould, there is produced a solution droplet that consistsof two separate regions each containing substantially only one of thepolymer solutions, either the uncoloured solution 6 or the colouredsolution 7.

The metering device shown in FIG. 3 differs from that shown in FIG. 2essentially only in the construction of the metering needle 2, which iswhy the holding block 20 has not been drawn in FIG. 3. The meteringneedle 2 shown in FIG. 3 is especially suitable for carrying out asecond embodiment of the process of the invention. Relative to thediameter of the inner nozzle 3 and to the annular diameter of the outer,annular nozzle 4, the partition wall 5 is thicker than in the meteringneedle shown in FIG. 2. As a result, the two polymer solutions can be sointroduced into the open casting mould 40 that the coloured polymersolution 7 and the uncoloured polymer solution 6 are substantiallyspatially separate in the open casting mould, typically being disposedin concentric annular regions as shown on an exaggerated scale in FIG.3.

In a third embodiment of the process of the invention, two separatemetering-in operations are carried out one after the other in the sameplace or spatially offset from each other. It is thereby possible, forexample, to introduce a coloured solution droplet into the open castingmould first and then cover it with the uncoloured polymer solution.

By suitably selecting the diameter and shape of the nozzles and themetering rates of the polymer solutions it is possible to manufacturecontact lenses having any desired concentric, annular regions ofdifferent colours. If the partition wall 5 between the inner nozzle 3and the outer, annular nozzle 4 is thin (corresponding to FIG. 2),slight mixing occurs at the contact surfaces of the two polymersolutions and the colour transitions in the contact lens are relativelyfluid. If the metering needle 2 shown in FIG. 3 is used, so that the twopolymer solutions are substantially spatially separate from each otherand run together only when the mould is closed, then a relativelysharply defined colour boundary results. FIGS. 4, 5, 6a and 7a showschematically examples of various colour distributions in the contactlenses, which can be obtained in the contact lenses using the mentionedthree embodiments of the process of the invention. The colourdistribution in the contact lens is produced only after closing of thecasting mould and is fixed in the closed casting mould by thecrosslinking of the polymer solutions.

FIG. 2 shows schematically inter alia a solution droplet in the opencasting mould 40 as produced by means of the metering needle 2 accordingto the mentioned first embodiment. The solution droplet consists of aregion containing the coloured polymer solution 7 and a regioncontaining the uncoloured polymer solution 6. As the polymer solutionsare being introduced into the open casting mould, the metering needle 2is moved in the direction of its longitudinal axis. That movement ismade in such a manner that the tip of the metering needle 2 is always atthe surface of the growing solution droplet throughout the introductionprocess. In FIG. 4, the corresponding colour distribution in the contactlens is shown. A coloured central region 8 is followed by a concentricannular region 9 that has a mixed coloration, and by a furtherconcentric annular region 10 that is colourless.

In FIG. 6, there can be seen a solution droplet that is also produced bycarrying out the first embodiment using the metering needle 2 shown inFIG. 2. In this case, however, the metering needle 2 is immersed in thegrowing solution droplet as the polymer solutions are being introducedinto the open casting mould. The corresponding colour distribution inthe contact lens is shown schematically in FIG. 6a. The central region11 has a mixed coloration. The adjoining concentric annular region 12 iscolourless and the outer concentric annular region 13 is coloured/has amixed coloration.

In FIG. 3, there is shown schematically inter alia a distribution of thetwo polymer solutions introduced into the open casting mould by means ofthe metering needle 2 in accordance with the mentioned secondembodiment. Before the casting mould is closed, the different polymersolutions are substantially spatially separate, in this example thecoloured polymer solution 7 being further towards the inside and thecolourless polymer solution 6 being further towards the outside. Thecolour distribution resulting therefrom in the contact lens is shownschematically in FIG. 5. The central region 14 is coloured and isseparated from the concentric colourless outer annular region 15 by arelatively sharply defined boundary.

The solution droplet shown in FIG. 7 is produced by means of thementioned third embodiment. In this case, two individual metering-inoperations are carried out separately in time. In this example, adroplet of the coloured polymer solution 7 is introduced into the opencasting mould first and that droplet is then covered with the uncolouredpolymer solution 6. The solution droplet accordingly consists of aregion containing the coloured polymer solution 7 and a region coveringthe latter and containing the uncoloured polymer solution 6. The colourdistribution resulting therefrom in the contact lens is shownschematically in FIG. 7a. The central region 16 has a mixed coloration.The adjoining, concentric annular region 17 is coloured and the outerannular region 18 has a mixed coloration.

In Table 2, a number of characteristic data of various process examplesare summarised. For comparison purposes, corresponding data ofcompletely uncoloured contact lenses are also given. The data are basedon a metering needle 2 having an inner nozzle 3 and an outer, annularnozzle 4 into which the coloured polymer solution and the uncolouredpolymer solution, respectively, are introduced from polypropylenedisposable syringes having a Luerlock connection. The colourless andcoloured polymer solutions are prepared as described above.

The first column contains a serial number for the individual processexamples. In the second and third columns of Table 2:

A is a sol charge consisting of crosslinkable modified PVA with a 30%solids content and 0.3% Irgacure 2959, which is substantiallycolourless;

B is a sol charge as A which, however, contains sufficient Duasyn Blauthat the dye concentration in the sol is 0.05%;

C is a sol charge as A which, however, contains sufficient Duasyn Blauthat the dye concentration in the sol is 0.1%.

In the fourth column, the Figure of the drawings in which therespectively used metering needle 2 is shown is indicated. The fifthcolumn indicates the Figure of the drawings which schematicallyreproduces the shape of the respectively introduced droplet; the sixthcolumn contains the Figure of the drawings which shows the colourdistribution of the respective contact lens. Columns 7 to 9 containgeometrical data of the contact lenses respectively obtained. In thosecolumns:

MT: is the thickness of the material in the centre of the contact lens(middle thickness)

DM: is the largest diameter of the contact lens

BC: is the radius of the base curve.

In the last line of the Table, provided with the serial number 19, datatypically obtained for completely uncoloured contact lenses manufacturedin the same casting mould are summarised for comparison purposes.

The polymer solutions are introduced, for example, by means ofseparately controllable pressure-metering systems Model 1000 XLE fromGLT GmbH. The metering pressure is from 3 to 5.5 bar.

For the manufacture of the contact lenses a male casting mould half madeof quartz glass (SQ1) and a female casting mould half made of Duranglass are used.

The irradiation is carried out by means of a UV lamp UVPRINT 300 CM fromDr. Honle GmbH using a 295 nm cut-off filter of 2 mm thickness fromSchott. The distance between the lamp housing and the cavity in thequartz mould is 14.5 cm. The light intensity in the range of from 280 to310 nm is 12.5 mW/m². The irradiation times are from 5 to 8 seconds.

In all the processes, the contact lenses manufactured are free ofdistortion. The transmission of the coloured contact lenses at 672 nm istypically 68% when using sol charge B (MT 0.095 mm) and 51.5% when usingsol charge C. The geometrical data of the partly coloured contact lensescorrespond to those of uncoloured contact lenses manufactured in thesame mould using only one material. In addition to reproducibility,Table 2 accordingly demonstrates the finding, which was not to beexpected by one skilled in the art, that partly coloured contact lensesor contact lenses having regions of different colours can bemanufactured by the process of the invention with the same precision andquality as uncoloured contact lenses.

                                      TABLE 1                                     __________________________________________________________________________       weighed in                                                                          Na.sub.2 CO.sub.3                                                                 pH value                                                                           weighed in                                                                          weighed in                                                                          pH value                                                                            0.01N                                                                             pH value                                 mod. PVA                                                                            0.5%                                                                              after                                                                              dye   H.sub.2 O                                                                           after HCl after HCl                             No.                                                                              [g] X [ml]                                                                              Na.sub.2 CO.sub.3                                                                  [mg] Y                                                                              [g] Z dye addition                                                                        [ml]                                                                              addition                              __________________________________________________________________________    1  30.0059                                                                             5.0 10.5 60.73 0.993 10.5  15  6.97                                  2  30.0038                                                                             5.0 10.5 29.87 1.052 10.5  15  6.98                                  __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________             metering                                                                           droplet                                                                           contact lens (CL)                                                    needle                                                                             shape                                                                             colour dis-                                                    sol                                                                              sol                                                                              acc. to                                                                            acc. to                                                                           tribution                                                                           MT    DM    BC                                        No.                                                                              inner                                                                            outer                                                                            Fig. Fig.                                                                              acc. to Fig.                                                                        [mm]  [mm]  [mm]                                      __________________________________________________________________________     1 B  A  2    6   6     0.080 14.00 8.65                                       2 C  A  2    6   6     0.083 14.00 8.60                                       3 C  A  2    6   6     0.083 14.00 8.60                                       4 C  A  2    6   6     0.082 13.95 8.65                                       5 C  A  2    6   6     0.080 14.05 8.55                                       6 A  C  2    6   6     0.082 14.00 8.50                                       7 A  C  2    6   6     0.081 13.95 8.45                                       8 C  A  2    6   6     0.083 14.05 8.50                                       9 C  A  2    7   7     0.080 14.00 8.45                                      10 C  A  2    7   7     0.084 14.00 8.40                                      11 C  A  2    7   7     0.089 14.05 8.55                                      12 C  A  2    7   7     0.097 14.10 8.50                                      13 C  A  2    7   7     0.090 14.00 8.55                                      14 C  A  2    7   7     0.085 13.95 8.55                                      15 C  A  3    3   5     0.078 13.95 8.55                                      16 C  A  2    7   7     0.081 13.95 8.55                                      17 C  A  2    7   7     0.081 14.00 8.50                                      18 C  A  2    7   7     0.079 13.90 8.60 MT - desired values:                 19 A  A  --   --  colourless                                                                          0.09-0.102                                                                          13.95-13.85                                                                         8.35-8.50                                            average value coloured CL:                                                                 0.083 14.00 8.54 coloured CL 0.085 mm                            average value colourless CL:                                                               0.093 13.91 8.57 colourless CL 0.095                  __________________________________________________________________________                                             mm                               

What is claimed is:
 1. A process for the manufacture of contact lensesthat are partly coloured or have regions of different colours, theprocess consisting essentially of the steps of introducing two or morecrosslinkable materials of different colours into an open casting mouldin an uncrosslinked state unmixed, wherein the crosslinkable materialsare placed in the mould as a droplet or droplets; closing the castingmould; and crosslinking the crosslinkable materials in the castingmould, wherein the crosslinkable materials are crosslinked by exposureto energy.
 2. A process according to claim 1, wherein the introductionof the crosslinkable materials is carried out in such a manner that theymix as little as possible in the casting mould.
 3. A process accordingto claim 2, wherein the crosslinkable materials are introduced into thecasting mould by means of coaxial metering nozzles.
 4. A processaccording to claim 3, wherein the coaxial metering nozzles are movedrelative to the casting mould during the introduction process.
 5. Aprocess according to claim 1, wherein the introduction of thecrosslinkable materials is carried out in such a manner that a droplethaving distinct regions is deposited in the mould, wherein each regionof the droplet contains substantially only one of the crosslinkablematerials.
 6. A process according to claim 1, wherein the introductionof the crosslinkable materials is carried out in such a manner that thedifferent crosslinkable materials are substantially spatially separatein the open casting mould.
 7. A process according to claim 1, whereinthe crosslinkable materials are introduced into the casting mouldsimultaneously.
 8. A process according to claim 1, wherein thecrosslinkable materials are introduced into the casting mould with apartial overlap in time.
 9. A process according to claim 1, wherein thecrosslinkable materials are introduced into the casting mould separatelyfrom each other in time.
 10. A process according to claim 1, wherein oneof the crosslinkable materials is substantially colourless.
 11. Aprocess according to claim 1, wherein the crosslinkable materials arewater-soluble polymers.
 12. A process according to claim 1, wherein thecrosslinkable materials of different colours that are introduced intothe casting mould in the uncrosslinked state unmixed are crosslinkedtogether.
 13. A process according to claim 1, wherein the crosslinkablematerials of different colours are exposed to energy simultaneously. 14.A process according to claim 11 wherein the crosslinkable materials arederivatives of polymeric 1,2- or 1,3 diols.
 15. A process according toclaim 12 wherein the crosslinkable materials are derivatives ofpolyvinyl alcohol or derivatives of copolymers of vinyl alcohol.
 16. Aprocess for the manufacture of contact lenses that are partly colouredor have regions of different colours, the process comprising the stepsof introducing two or more crosslinkable materials of different coloursinto an open casting mould in an uncrosslinked state unmixed, whereinthe crosslinkable materials are placed in the mould by means of coaxialmetering nozzles; closing the casting mould; and crosslinking thecrosslinkable materials in the casting mould, wherein the crosslinkablematerials are crosslinked by exposure to energy.